1,011 research outputs found
Frequency stability of a wavelength meter and applications to laser frequency stabilization
Interferometric wavelength meters have attained frequency resolutions down to
the MHz range. In particular, Fizeau interferometers, which have no moving
parts, are becoming a popular tool for laser characterization and
stabilization. In this article, we characterize such a wavelength meter using
an ultra-stable laser in terms of relative frequency instability
and demonstrate that it can achieve a short-term instability
and a frequency drift of order
MHz/day. We use this apparatus to demonstrate frequency control of a
near-infrared laser, where a frequency instability below
from 1 s to 2000 s is achieved. Such performance is for example adequate for
ions trapping and atoms cooling experiments.Comment: 5 pages, 4 figure
Le soutien social des personnes ĂągĂ©es au carrefour des services de lâĂtat
Cet article prĂ©sente les rĂ©sultats d'une recherche menĂ©e auprĂšs de personnes ĂągĂ©es dans la MunicipalitĂ© rĂ©gionale de comtĂ© de Pabok en GaspĂ©sie. Les auteurs discutent de la prĂ©pondĂ©rance des facteurs tenant au soutien naturel (en particulier celui de la famille) et Ă l'environnement social dans l'orientation des personnes ĂągĂ©es vers les Ă©tablissements de services publics. Ils se penchent en outre sur la nĂ©cessitĂ© de repenser l'articulation entre services formels et informels dans la perspective d'une plus grande complĂ©mentaritĂ© entre eux et d'un soutien accru de l'Ătat aux aidants naturels. Des pistes d'intervention sont Ă©galement suggĂ©rĂ©es; elles portent tout particuliĂšrement sur le dĂ©veloppement de services de soutien Ă domicile et de rĂ©pit visant Ă soutenir les aidants naturels oeuvrant auprĂšs de personnes ĂągĂ©es en perte d'autonomie
La configuration des corrélations entre le concept de soi et le rendement scolaire : une méta-analyse
Cet article présente la problématique, la méthodologie et les résultats d'une méta-analyse de la configuration du lien corrélatif entre le concept de soi et le rendement scolaire. Il ressort de la recherche que la caractérisation des diverses catégories de concept de soi et de rendement scolaire constitue un premier facteur explicatif de ce lien. La configuration proposée permet de conclure que le concept de soi non scolaire et le concept de soi général ont des corrélations faibles alors que le concept de soi scolaire présente des liens nettement plus élevés variant selon les types de rendement scolaire de moyen à modérément élevé. Le rejet de l'hypothÚse d'homogénéité des corrélations de chaque catégorie soulÚve la possibilité de l'existence de variables concomitantes constituant un deuxiÚme facteur explicatif.This article presents the theoretical frame, the methodology, and the results of a meta-analysis of the correlational structure between self-concept and school achievement. The authors found that the classification of different categories of self-concept and of school achievement was the first factor to account for this correlation. Among the conclusions, the authors note that scores relating to non-school self-concept and general self-concept provide weak correlations while specific school self-concept presents higher relationships which vary from average to moderate-high according to the types of school success examined. Finally, they reject the hypothesis of homogeneity of correlations for each category, which raises the possibility of the existence of other variables constituting a second factor.Este articulo présenta la problemà tica, la metodologia y los resultados de un meta analisis de la configuracion de la relacion correlativa entre el concepto de si mismo y el rendimiento académico. Un resultado del estudio es que la caracterizacion de las distintas categorias de concepto de si y de rendimiento académico constituye un primer factor expli-cativo de esta relacion. La configuracion propuesta permite concluir que el concepto de si "no-escolar" y el concepto de si "general" tienen correlaciones bajas mientras que el concepto de si académico présenta lazos netamente mas fuertes que varian de medio a moderadamente elevados segûn los tipos de rendimiento académico. El rechazo de la hipotesis de la homoge-neidad de correlaciones de cada categoria expone la posibilidad de la existencia de variables concomitantes que constituinan un segundo factor explicativo.Der vorliegende Artikel erÎrtert die Problematik, die Méthode und die Ergebnisse einer Meta-Analyse der Struktur des korrelativen Zusammenhangs zwischen Selbstgefuhl und schulischer Leistung. Es ergibt sich, dass die Charakterisierung der verschie-denen Kategorien von Selbstgefuhl und von schulischer Leistung den ersten Ansatz zu einer Erlà uterung dieses Zusammenhangs darstellt. Die vorgeschlagene Struktur fiihrt zu der Schlussfolgerung, dass das schulunabhà ngige und das allgemeine Selbstgefuhl nur schwache Korrelationen aufweisen, wohingegen das schulbezogene Selbstgefuhl je nach mittelbis mittelhoher Leistung in weitaus stà rkerem 2!!usammenhang mit der Leistung steht. Die Ablehnung der HypothÚse einer Homogenitùt der Korrelationen jeder Kategorie fiihrt zu der mÎglichen Existenz von gleichzeitigen Variablen, die einen weiteren erlùuternden Faktor darstellen
Shortcomings of an idealized urbanity : ghost urban areas and the asynchronous territorial development of Hanoi
This paper examines the recent emergence, on the periphery of Hanoi,
of large real estate projects that began construction during the 2000s but have now
remained unfinished or, even when completed, largely uninhabited. These âghost urban
areas,â as the local press calls them, epitomize some of the problems which emerged in
Hanoi when a model of urban development that aimed at realizing an imagined urban
future, formulated by state planning agencies, encountered the highly speculative reality
of Vietnamâs property market. Ghost urban areas reveal how the stateâs planning
orientations and discourseâconveying ideals of urban âmodernity,â âcivility,â and
particularly âsynchronyââinstead generated dysfunctional, incomplete, and disconnected
places. Based on a survey of thirty-nine ghost urban areas, a cartographic analysis,
interviews with key actors, and a critical study of policy documents, this paper reveals
multiple scales and forms of what we call âasynchronous territorial developments.â
Around Hanoi, these developments involve vast tracts of agricultural lands forcibly
appropriated yet left fallow, planned infrastructure and amenities that stay unbuilt for
indefinite periods of time, and housing units transacted multiple times among speculators
but have remained largely uninhabited and out of reach for a majority of urban
households. Ultimately, we interrogate how these various territorial asynchronies, both
generated by and plaguing ghost urban areas, shape their livability and inhabitantsâ
experience
Le cybertransport : une clé pour un développement responsable
International audienceLes cybertransports sont une avenue pour amĂ©liorer la mobilitĂ© des marchandises et des personnes. Parmi les technologies disponibles, la Serpentine, en tant que systĂšme de transport cybernĂ©tique, se distingue par ses propriĂ©tĂ©s structurelles et sa capacitĂ© intrinsĂšque Ă rĂ©pondre collectivement Ă des besoins individuels. DĂšs lors, le mode opĂ©ratoire des vĂ©hicules doit ĂȘtre dĂ©veloppĂ© afin d'exploiter ces propriĂ©tĂ©s. L'analogie avec les rĂ©seaux Ă©lectriques ainsi que l'intĂ©gration du principe d'entropie permet de dĂ©finir une rĂšgle comportementale du systĂšme pour rĂ©pondre Ă la demande des usagers. Le scĂ©nario synthĂ©tique dĂ©veloppĂ© pour le centre-ville de MontrĂ©al montre que le modĂšle dynamique permet, lors d'une forte demande, d'assurer la pĂ©rennitĂ© du service et l'intĂ©gritĂ© du systĂšme. Par ailleurs, l'intĂ©gration de la Serpentine dans un milieu urbain comme MontrĂ©al permet, comparativement au tramway, d'amĂ©liorer l'offre de service par une mobilitĂ© de proximitĂ© de type multiples-multiples. De plus, le partage de l'infrastructure pour la livraison des marchandises permet de rĂ©partir les charges et ainsi offrir un service disponible Ă tous
Compact Yb optical atomic clock project: design principle and current status
We present the design of a compact optical clock based on the 435.5 nm transition in Yb. The ion trap will
be based on a micro-fabricated circuit, with surface electrodes generating a
trapping potential to localize a single Yb ion a few hundred m from the
electrodes. We present our trap design as well as simulations of the resulting
trapping pseudo-potential. We also present a compact, multi-channel wavelength
meter that will permit the frequency stabilization of the cooling, repumping
and clear-out lasers at 369.5 nm, 935.2 nm and 638.6 nm needed to cool the ion.
We use this wavelength meter to characterize and stabilize the frequency of
extended cavity diode lasers at 369.5 nm and 638.6 nm.Comment: 7 pages, 5 figures. Proc. of the 8th FSM 2015, Potsdam, Germany. To
be published in IOP Journal of Physics: Conference Serie
A self-inactivating retrovector incorporating the IL-2 promoter for activation-induced transgene expression in genetically engineered T-cells
BACKGROUND: T-cell activation leads to signaling pathways that ultimately result in induction of gene transcription from the interleukin-2 (IL-2) promoter. We hypothesized that the IL-2 promoter or its synthetic derivatives can lead to T-cell specific, activation-induced transgene expression. Our objective was to develop a retroviral vector for stable and activation-induced transgene expression in T-lymphocytes. RESULTS: First, we compared the transcriptional potency of the full-length IL-2 promoter with that of a synthetic promoter composed of 3 repeats of the Nuclear Factor of Activated T-Cells (NFAT) element following activation of transfected Jurkat T-cells expressing the large SV40 T antigen (Jurkat TAg). Although the NFAT3 promoter resulted in a stronger induction of luciferase reporter expression post stimulation, the basal levels of the IL-2 promoter-driven reporter expression were much lower indicating that the IL-2 promoter can serve as a more stringent activation-dependent promoter in T-cells. Based on this data, we generated a self-inactivating retroviral vector with the full-length human IL-2 promoter, namely SINIL-2pr that incorporated the enhanced green fluorescent protein (EGFP) fused to herpes simplex virus thymidine kinase as a reporter/suicide "bifunctional" gene. Subsequently, Vesicular Stomatitis Virus-G Protein pseudotyped retroparticles were generated for SINIL-2pr and used to transduce the Jurkat T-cell line and the ZAP-70-deficient P116 cell line. Flow cytometry analysis showed that EGFP expression was markedly enhanced post co-stimulation of the gene-modified cells with 1 ÎŒM ionomycin and 10 ng/ml phorbol 12-myristate 13-acetate (PMA). This activation-induced expression was abrogated when the cells were pretreated with 300 nM cyclosporin A. CONCLUSION: These results demonstrate that the SINIL-2pr retrovector leads to activation-inducible transgene expression in Jurkat T-cell lines. We propose that this design can be potentially exploited in several cellular immunotherapy applications
Faunal and Archaeological Remains as Evidence of Climate Change in Freezing Caverns, Yukon Territory, Canada
Animal and plant remains, some associated with prehistoric artifacts, were collected in freezing caverns (glaciÚres) of northern Yukon Territory. Radiocarbon dates show that the oldest remains are Middle Wisconsinan ca. 38 000 BP). The absence of material of Late Wisconsinan age likely indicates that the caves were infilled by ice during this cold period. Climate warming and ice melting during the Holocene allowed animals and prehistoric hunters to regularly visit these caves. Ice plugs were evidently smaller during the early Holocene than they are now.Des restes d'animaux et de plantes, parfois associés à des vestiges préhistoriques, ont été récoltés dans des glaciÚres du nord du Territoire du Yukon. Leur ùge radiocarbone indique que les plus anciens vestiges datent du Wisconsinien moyen (v. 38 000 BP). L'absence de matériel contemporain du Wisconsinien supérieur semble indiquer que pendant cette période froide les cavernes étaient comblées par de la glace. Au cours de l'HolocÚne, le réchauffement du climat et la fonte subséquente des glaces ont permis aux animaux et aux chasseurs préhistoriques de visiter les cavernes sur une base réguliÚre. Les bouchons de glace étaient de toute évidence moins développés au début de l'HolocÚne qu'ils ne le sont aujourd'hui
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